JP7248677B2 - Process for producing nitrile rubber using ruthenium complex catalyst - Google Patents

Description

The present invention provides a first method of producing a first ruthenium complex catalyst in the presence of a particular ruthenium complex catalyst having, in particular, N-heterocyclic carbene ligands, and in particular bridged carbene ligands having at least one electron-withdrawing group. It relates to a process for metathesizing nitrile rubber to prepare nitrile rubber with reduced molecular weight.

Metathesis reactions are, in the context of chemical synthesis, e.g. reactions, reactions of alkenes with alkynes (ene-yne reactions), polymerization of alkynes, and olefination reactions of carbonyls. Metathesis reactions are employed, for example, for the synthesis of olefins, for the ring-opening polymerization of norbornene derivatives, for the depolymerization of unsaturated polymers, and for the synthesis of telechelics.

A wide variety of titanium-, tungsten-, molybdenum-, ruthenium-, and osmium-based catalysts are available for catalyzing these reactions and are described, for example, in There are: Katz (Non-Patent Document 1), Bassett (Non-Patent Document 2), Schrock ((Non-Patent Document 3); (Non-Patent Document 4); (Non-Patent Document 5)), Grubbs ((Patent Document 1); (Patent Document 2); (Patent Document 3)), Herrmann (Non-Patent Document 6), Hoveyda (Patent Document 4), Hill-Fuerstner ((Non-Patent Document 7); (Non-Patent Document 8)), Fogg (Non-Patent Document Patent Document 9), Buchmeiser-Nuyken ((Non-Patent Document 10); (Non-Patent Document 11)), Nolan (Patent Document 5), Dixneuf (Patent Document 6), Mol (Non-Patent Document 12), Wagener (Non-Patent Document Document 13), Piers (Patent Document 7), Grela (Patent Document 8), Barbasiewicz (Non-Patent Document 14), Mauduit (Patent Document 9), Arlt (Patent Document 10), Berke (Patent Document 11), Zahn (( Patent Documents 12), (Patent Document 13)), and Ciba Special Chemicals ((Patent Document 14); (Patent Document 15)), and Boehringer Ingelheim ((Non-Patent Document 15); (Non-Patent Document 16)).

The catalysts described vary in their suitability for the various aforementioned metathesis reactions. The above-mentioned catalysts are not necessarily suitable for catalyzing metathesis reactions of substrates with polar groups, especially nitrile groups, because few metathesis catalysts are tolerant of polar groups. In the metathesis of nitrile rubber, the choice of a suitable catalyst is further restricted in that nitrile rubbers prepared by emulsion polymerization on an industrial scale contain not only nitrile groups but also process-specific Impurities such as initiators, redox systems, chain transfer agents, fatty acids, or antioxidants are included and act as catalyst poisons. A further difficulty or danger is that nitrile rubber easily gels and renders the polymer insoluble, thereby further limiting its field of use. Moreover, the polymer can no longer be mixed well, resulting in defects in the final product.

Catalysts which are in principle suitable for the metathesis of nitrile rubbers and which meet the above criteria to various levels are described, for example, in the following patents: US Pat. ), US Pat.

［式中、
Ｍは、ルテニウム又はオスミウムであり、
Ｙは、酸素（Ｏ）、硫黄（Ｓ）、Ｎ－Ｒ^１基若しくはＰ－Ｒ^１基（ここで、Ｒ^１は以下に述べる定義を有する）であり、
Ｘ^１及びＸ^２は、同一であっても異なっていてもよい配位子を表し、
Ｒ^１は、アルキル、シクロアルキル、アルケニル、アルキニル、アリール、アルコキシ、アルケニルオキシ、アルキニルオキシ、アリールオキシ、アルコキシカルボニル、アルキルアミノ、アルキルチオ、アリールチオ、アルキルスルホニル、又はアルキルスルフィニル基を表すが、それらはすべて、それぞれ任意選択により場合によっては、１個又は複数のアルキル、ハロゲン、アルコキシ、アリール又はヘテロアリール基によって置換されていてもよく、
Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５は、同一であっても異なっていてもよく、水素又は有機若しくは無機の基を表し、
Ｒ^６は、水素又はアルキル、アルケニル、アルキニル若しくはアリール基であり、そして
Ｌは、配位子である。］ US Pat. No. 6,200,400 describes a Grubbs-Hoveyda II type transition metal-carbene complex catalyst having the following general structure (I) for the metathesis of nitrile rubbers:

[In the formula,
M is ruthenium or osmium,
Y is oxygen (O), sulfur (S), an NR ¹ group or a PR ¹ group, wherein R ¹ has the definition set forth below;
X ¹ and X ² represent ligands that may be the same or different,
R ¹ represents an alkyl, cycloalkyl, alkenyl, alkynyl, aryl, alkoxy, alkenyloxy, alkynyloxy, aryloxy, alkoxycarbonyl, alkylamino, alkylthio, arylthio, alkylsulfonyl or alkylsulfinyl group, all of which are , each optionally substituted by one or more alkyl, halogen, alkoxy, aryl or heteroaryl groups;
R ² , R ³ , R ⁴ and R ⁵ , which may be the same or different, represent hydrogen or an organic or inorganic group;
^R6 is hydrogen or an alkyl, alkenyl, alkynyl or aryl group and L is a ligand. ]

In the catalyst of general formula (I), L is a ligand, typically a ligand with electron donor functionality. L can represent a P(R ⁷ ) ₃ group, where R ⁷ is independently C ₁ -C ₆ -alkyl, C ₃ -C ₈ -cycloalkyl, or aryl, or so If not, it is an optionally optionally substituted imidazolidine group (“Im”).

［式中、
Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１は、同一であっても異なっていてもよく、以下のものである：水素、直鎖状若しくは分岐状のＣ_１～Ｃ_３０－アルキル、好ましくはＣ_１～Ｃ_２０－アルキル、Ｃ_３～Ｃ_２０－シクロアルキル、好ましくはＣ_３～Ｃ_１０－シクロアルキル、Ｃ_２～Ｃ_２０－アルケニル、好ましくはＣ_２～Ｃ_１０－アルケニル、Ｃ_２～Ｃ_２０－アルキニル、好ましくはＣ_２～Ｃ_１０－アルキニル、Ｃ_６～Ｃ_２４－アリール、好ましくはＣ_６～Ｃ_１４－アリール、Ｃ_１～Ｃ_２０－カルボキシレート、好ましくはＣ_１～Ｃ_１０－カルボキシレート、Ｃ_１～Ｃ_２０－アルコキシ、好ましくはＣ_１～Ｃ_１０－アルコキシ、Ｃ_２～Ｃ_２０－アルケニルオキシ、好ましくはＣ_２～Ｃ_１０－アルケニルオキシ、Ｃ_２～Ｃ_２０－アルキニルオキシ、好ましくはＣ_２～Ｃ_１０－アルキニルオキシ、Ｃ_６～Ｃ_２０－アリールオキシ、好ましくはＣ_６～Ｃ_１４－アリールオキシ、Ｃ_２～Ｃ_２０－アルコキシカルボニル、好ましくはＣ_２～Ｃ_１０－アルコキシカルボニル、Ｃ_１～Ｃ_２０－アルキルチオ、好ましくはＣ_１～Ｃ_１０－アルキルチオ、Ｃ_６～Ｃ_２０－アリールチオ、好ましくはＣ_６～Ｃ_１４－アリールチオ、Ｃ_１～Ｃ_２０－アルキルスルホニル、好ましくはＣ_１～Ｃ_１０－アルキルスルホニル、Ｃ_１～Ｃ_２０－アルキルスルホネート、好ましくはＣ_１～Ｃ_１０－アルキルスルホネート、Ｃ_６～Ｃ_２０－アリールスルホネート、好ましくはＣ_６～Ｃ_１４－アリールスルホネート、及びＣ_１～Ｃ_２０－アルキルスルフィニル、好ましくはＣ_１～Ｃ_１０－アルキルスルフィニル。 The imidazolidine group (Im) typically has the structure of general formula (IIa) or (IIb).

[In the formula,
R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , which may be identical or different, are hydrogen, linear or branched C ₁ -C ₃₀ -alkyl, preferably C ₁ - _C20 -alkyl, _C3 - _C20 -cycloalkyl, preferably _C3 - _C10 -cycloalkyl, _C2 - _C20 -alkenyl, preferably C2 _{- C10} -alkenyl, _C2 - _C20 -alkynyl, preferably C ₂ -C ₁₀ -alkynyl, C ₆ -C ₂₄ -aryl, preferably C ₆ -C ₁₄ -aryl, C ₁ -C ₂₀ -carboxylate, preferably C ₁ -C ₁₀ -carboxylate , C ₁ -C ₂₀ -alkoxy, preferably C ₁ -C ₁₀ -alkoxy, C ₂ -C ₂₀ -alkenyloxy, preferably C ₂ -C ₁₀ -alkenyloxy, C ₂ -C ₂₀ -alkynyloxy, preferably C ₂ -C ₁₀ -alkynyloxy, C ₆ -C ₂₀ -aryloxy, preferably C ₆ -C ₁₄ -aryloxy, C ₂ -C ₂₀ -alkoxycarbonyl, preferably C ₂ -C ₁₀ -alkoxycarbonyl, C ₁ -C ₂₀ -Alkylthio, preferably C ₁ -C ₁₀ -alkylthio, C ₆ -C ₂₀ -arylthio, preferably C ₆ -C ₁₄ -arylthio, C ₁ -C ₂₀ -alkylsulfonyl, preferably C ₁ -C ₁₀ -alkylsulfonyl, C ₁ -C ₂₀ -alkylsulfonates, preferably C ₁ -C ₁₀ -alkylsulfonates, C ₆ -C ₂₀ -arylsulfonates, preferably C ₆ -C ₁₄ -arylsulfonates, and C ₁ -C ₂₀ -alkylsulfinyl, preferably C ₁ -C ₁₀ -alkylsulfinyl.

Particularly preferred imidazolidine groups (Im) have the following structures (IIIa-IIIf), wherein Mes is in each case a 2,4,6-trimethylphenyl group:

The specifically described catalysts are of the following structures, where Mes is in each case 2,4,6-trimethylphenyl:

Hoveyda-type catalysts allow cross metathesis of nitrile rubbers in the presence of 1-olefins with Ru inputs ranging from 8.6 ppm to 161 ppm based on nitrile rubber. In the Ru loading range of 8.6-23.8 ppm, the Hoveyda and Grela catalysts have higher activity than the Grubbs II catalyst (G II) at the same Ru loading. The teaching of WO 2005/010303 does not reveal what structural characteristics the catalyst must have in order to be able to further improve its efficiency in the metathesis of nitrile rubber. More specifically, design details regarding NHC substituents and aromatic carbene ligands are lacking.

明示されているのは次の触媒である：

US Pat. No. 6,300,302 describes catalysts with the following general structural characteristics:

Specified are the following catalysts:

At comparable Ru loadings, these catalysts have higher activity than the Grubbs II catalyst.

A disadvantage of the catalysts described in WO 2005/010002 for the metathesis of nitrile rubbers is that their catalytic activity is too low for commercial use.

明示されているのは次のフルオレニリデン錯体触媒である：

US Pat. No. 6,200,000 describes transition metal-carbene complex catalysts with the following structural characteristics:

Specified are the following fluorenylidene complex catalysts:

The fluorenylidene complexes have a broad spectrum of uses and can be used in a wide variety of metathesis reactions, including the decomposition of nitrile rubbers. However, their activity is insufficient for nitrile rubber metathesis.

The Arlt catalysts described in US Pat. No. 5,300,000 are used in US Pat.

In US Pat. Nos. 5,400,002 and 5,001,001 Arlt's catalyst is compared to Grubbs II catalyst at three loadings of 0.003 phr, 0.007 phr, and 0.15 phr. In six experiments the degradation of nitrile rubber was performed as cross metathesis in the presence of 4 phr of 1-hexene. Compared to the Grubbs II catalyst, the Arlt catalyst gives lower molar masses (M _w and M _n ) than the Grubbs II catalyst. (Patent Document 18) does not compare the activity of the Arlt catalyst with the activity of the Grubbs-Hoveyda II catalyst (GH II), but from (Patent Document 16), the Grubbs-Hoveyda II catalyst (GH II) It is known to have higher activity than the Grubbs II catalyst. In addition, the teaching of WO 2005/030000 does not reveal how the chemical structure of the metathesis catalyst should be changed in order to have higher activity in the metathesis of nitrile rubber than the Grubbs-Hoveyda catalyst.

US Pat. No. 5,300,000 describes a number of catalysts with monodentate and bidentate N-containing ligands and O-containing ligand systems, which ligands are , in each case attached to the carbon carbene at the o-position of the aromatic system. Applications of these catalysts include RCM and ROMP implementations, but are not compared to known catalysts, so no relative assessment of catalytic activity is possible. Further, metathesis and hydrogenation of double bond-containing rubbers such as nitrile rubber (NBR), styrene/butadiene rubber (SPR and SBS), and butyl rubber (IIR) are described, but metathesis and hydrogenation are It can be performed sequentially or simultaneously. Examples are disclosed for the metathesis of commercial nitrile rubbers and for simultaneous metathesis and hydrogenation. Using 0.04 wt%, 0.07 wt%, and 0.1 wt% of catalyst 4aa in chloroform or chlorobenzene at a temperature in the range of 30°C to 100°C without using a 1-olefin , carrying out its metathesis. Metathesis and hydrogenation are carried out simultaneously using catalyst 4ab and using the same amount of catalyst.

Even based on the details of WO 2005/010002, it is not possible to make any predictions about the optimization of the ligand system for metathesis reactions, more specifically for metathesis of nitrile rubbers.

The catalysts described in connection with metathesis in the above-mentioned patent specifications are able to tolerate nitrile rubbers and impurities present in the nitrile rubbers. However, the activity of those catalysts is insufficient from a cost point of view.

［式中、
Ｌは、電荷を持たない配位子であり、
Ｘ及びＸ’は、アニオン性配位子を表し、
Ｒ^１及びＲ^２は、独立して、以下のものであり：Ｈ、Ｃ_１～Ｃ_６－アルキル、ペルハロゲン化Ｃ_１～Ｃ_６－アルキル、アルデヒド、ケトン、エステル、アミド、ニトリル、任意選択により場合によっては置換されたアリール、ピリジニウム－アルキル、ピリジニウム－ペルハロアルキル、又は任意選択により場合によっては置換されたＣ_５～Ｃ_６シクロヘキシル、Ｃ_ｎＨ_２ｎＹ若しくはＣ_ｎＦ_２ｎＹ基（ｎ＝１～６、そしてＹは、次式のうち１つのイオン性の基又はラジカルを表す）

Ｒ^３は、Ｃ_１～Ｃ_６－アルキル、又はＣ_５～Ｃ_６－シクロアルキル、又はＣ_５～Ｃ_６－アリールであり、
Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１は、独立して、Ｈ、Ｃ_１～Ｃ_６－アルキル、Ｃ_１～Ｃ_６－ペルハロアルキル、又はＣ_５～Ｃ_６－アリールであり、
Ｒ^９、Ｒ^１０、Ｒ^１１は、複素環を形成してもよく、
Ｘ^１は、アニオン、ハロゲン、テトラフルオロボレート（［ＢＦ_４］^－）、［テトラキス－（３，５－ビス（トリフルオロメチル）フェニル）ボレート］（［ＢＡＲＦ］^－）、ヘキサフルオロホスフェート（［ＰＦ_６］^－）、ヘキサフルオロアンチモネート（［ＳｂＦ_６］^－）、ヘキサフルオロアルセネート（［ＡｓＦ_６］^－）、トリフルオロメチルスルホネート（［（ＣＦ_３）_２Ｎ］^－）であり；
Ｒ^１及びＲ^２は、それらが結合されているＮ及びＣと共に、次式の複素環を形成してもよく、

（式中、
ｈａｌは、ハロゲンであり、そしてＲ^１２は、水素、Ｃ_１～Ｃ_６－アルキル、Ｃ_５～Ｃ_６－シクロアルキル、又はＣ_５～Ｃ_６－アリールである。）］ US Pat. No. 6,201,400 describes a substituted catalyst of the Grubbs-Hoveyda II type (hereafter referred to as "Mauduit catalyst") with the following structural characteristics:

[In the formula,
L is an uncharged ligand,
X and X' represent an anionic ligand,
R ¹ and R ² are independently: H, C ₁ -C ₆ -alkyl, perhalogenated C ₁ -C ₆ -alkyl, aldehydes, ketones, esters, amides, nitriles, optional aryl, pyridinium-alkyl, pyridinium-perhaloalkyl optionally substituted with, or optionally substituted C ₅ -C ₆ cyclohexyl, C _n H _2n Y or C _n F _2n Y groups where n= 1-6, and Y represents an ionic group or radical of one of the following formulas:

R ³ is C ₁ -C ₆ -alkyl, or C ₅ -C ₆ -cycloalkyl, or C ₅ -C ₆ -aryl,
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ are independently H, C ₁ -C ₆ -alkyl, C ₁ -C ₆ -perhaloalkyl, or C ₅ - _C6 -aryl,
R ⁹ , R ¹⁰ and R ¹¹ may form a heterocyclic ring,
X ¹ is an anion, halogen, tetrafluoroborate ([BF ₄ ] ⁻ ), [tetrakis-(3,5-bis(trifluoromethyl)phenyl)borate] ([BARF] ⁻ ), hexafluorophosphate ([PF ₆ ] ⁻ ), hexafluoroantimonate ([SbF ₆ ] ⁻ ), hexafluoroarsenate ([AsF ₆ ] ⁻ ), trifluoromethylsulfonate ([(CF ₃ ) ₂ N] ⁻ );
R ¹ and R ² together with the N and C to which they are attached may form a heterocyclic ring of the formula

(In the formula,
hal is halogen and R ¹² is hydrogen, C ₁ -C ₆ -alkyl, C ₅ -C ₆ -cycloalkyl or C ₅ -C ₆ -aryl. )]

In one preferred embodiment, L is P(R ¹³ ) ₃ , where R ¹³ is C ₁ -C ₆ -alkyl, C ₅ -C ₆ -aryl, or C ₅ -C ₆ - is cycloalkyl.

式中、ｎ^１＝０、１、２、３であり；
Ｒ^１４、Ｒ^１５、Ｒ^１６、Ｒ^１７、Ｒ^１８、Ｒ^１９、Ｒ^２０、Ｒ^２１、Ｒ^２２、Ｒ^２３、Ｒ^２４、Ｒ^２５、Ｒ^２６、Ｒ^２７、Ｒ^２８は、独立して、Ｃ_１～Ｃ_６－アルキル、Ｃ_３～Ｃ_２０－シクロアルキル、Ｃ_２～Ｃ_２０－アルケニル、ナフチル、アントラセン、又はフェニルであるが、ここで、そのフェニルは、任意選択により場合によっては、Ｃ_１～Ｃ_６－アルキル、Ｃ_１～Ｃ_６－アルコキシ、及びハロゲンを含む群から選択される最大５個の基によって置換されていてもよく、
Ｒ^１６とＲ^１７、並びにＲ^２６とＲ^２７は、３、４、５、６、又は７個の結合を有する環を形成してもよく、
Ｒ^２８は、独立して、６個の結合を有する芳香族環を形成してもよい。 In alternative preferred embodiments, L is a ligand of formula 7a, 7b, 7c, 7d, or 7e:

wherein n ¹ = 0, 1, 2, 3;
^R14 , ^{R15 , R16 , R17} , ^R18 , R19, R20, ^R21 , ^R22 , ^R23 , ^R24 , ^R25 , ^R26 , ^R27 and ^R28 are independently C ₁ -C ₆ -alkyl, C ₃ -C ₂₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl, naphthyl, anthracene, or phenyl, wherein the phenyl is optionally C optionally substituted by up to 5 groups selected from the group comprising ₁ - _C6 -alkyl, _C1 - _C6 -alkoxy and halogen;
R ¹⁶ and R ¹⁷ and R ²⁶ and R ²⁷ may form a ring having 3, 4, 5, 6 or 7 bonds;
R ²⁸ may independently form an aromatic ring with 6 bonds.

Selected Mauduit catalysts are, for example:

Mauduit catalysts have the characteristic of being easily recycled, which makes it possible to prepare metathesis reaction products with low precious metal contents. In the most preferred case, Mauduit catalysts allow the preparation of reaction products having a ruthenium content of less than 10 ppm to 20 ppm.

No mention is made of nitrile rubber metathesis in US Pat. In addition, WO 2005/010003 lacks guidance on optimizing the catalyst structure, especially the structure of the NHC ligand, to reduce the amount of catalyst in the metathesis of nitrile rubber. WO 2005/010303 likewise contains no guidance as to whether it is possible to accelerate the metathesis reaction of nitrile rubber by adding additives.

Furthermore, the patent literature describes a number of additives with which it is possible to improve the activity of metathesis catalysts, in particular for the metathesis of nitrile rubber (US Pat. Document 22), (Patent Document 23), (Patent Document 17), (Patent Document 24), (Patent Document 25), (Patent Document 26)).

These patents describe the use of salts such as lithium chloride, lithium bromide, magnesium chloride, calcium chloride, etc., as well as compounds such as borate esters, tri Boron fluoride-ether adducts, transition metal esters such as tetraalkoxy titanates. However, from these patent specifications it is not clear what structural characteristics the ruthenium- or osmium-containing transition metal complexes must have in order to have a particularly high activity in nitrile rubber metathesis. Impossible to guess.

WO A00/71554 pamphlet WO A2007/08198 pamphlet WO A03/011455 pamphlet U.S. Patent Application Publication No. A2002/0107138 WO A00/15339 pamphlet WO 1999/28330 pamphlet WO A2005/121158 Pamphlet WO A2004/035596 pamphlet WO A2008/065187 pamphlet WO A2008/034552 pamphlet EP-A2027920 U.S. Patent Application Publication No. A2007/0043180 WO A2011/079439 pamphlet EP-A0993465 EP-A0839821 EP-A1826220 EP-A2028194 EP-A2289622 EP-A2289623 WO A2011/079799 pamphlet EP-A1760093 EP-A1894946 EP-A2027919 EP-A2030988 EP-A2143489 EP-A2147721

Katz: Tetrahedron Lett. , 47, 4247-4250 (1976) Bassett: Angew. Chem. Int. Ed. , 31, 628-631 (1992) Schrock:J. Am. Chem. Soc. , 108, 2271-2273 (1986) Schrock: Catal. , 46, 243-253 (1988) Schrock: Organometallics, 9, 2262-2275 (1990) Herrmann: Angew. Chem. Int. Ed. , 37, 2490-2493 (1998) Hill-Fuerstner:J. Chem. Soc. Dalton Trans. , 1999, 285-291 Hill-Fuerstner: Chem. Eur. J. , 2001, 7, No. 22, 4811-4820 Fogg: Organometallics, 2003, 22, 3634 Buchmeiser-Nuyken: Macromol. Symp. , 2004, 217, 179-190 Buchmeiser-Nuyken: Chem. Eur. J. , 2004, 10, 777-784 Mol:J. C. Adv. Synth. Catal. , 2002, 344, 671-677 Wagener: Macromolecules, 2003, 36, 8231, 8239 Barbasiewicz: Organometallics, 2012, 31, 3171-3177 Boehringer Ingelheim: Org. Process Res. Dev. , 2005, 9, 513 Boehringer Ingelheim:J. Org. Chem. , 2006, 71, 7133

The problem addressed by the present invention is therefore to have a higher activity than the known catalysts, in particular of the Grubbs II, Grubbs III or Grubbs-Hoveyda II type, and to produce gels very substantially. To provide a catalyst-based process for the metathesis of nitrile rubbers, especially commercial nitrile rubbers, which allows molecular weight reduction without increasing the PDI.

Surprisingly, ruthenium complex catalysts comprising bridged carbene ligands having at least one electron-withdrawing group (EWG) are characterized in that these ruthenium complex catalysts are sterically It has been found that the desired performance requirements are met when the NHC ligand further comprises two phenyl rings substituted by two phenyl rings each having sterically demanding substituents.

［式中、
Ｘ^１及びＸ^２は、同一であっても異なっていてもよく、アニオン性配位子、好ましくはハロゲン、より好ましくはＦ、Ｃｌ、Ｂｒ、Ｉ、特に好ましくはＣｌを表し、
Ｒ^１は、直鎖状又は分岐状の脂肪族のＣ_１～Ｃ_２０－アルキル、Ｃ_３～Ｃ_２０－シクロアルキル、Ｃ_５～Ｃ_２０－アリール、ＣＨＣＨ_３－ＣＯ－ＣＨ_３、好ましくはメチル、エチル、イソプロピル、イソアミル、ｔ－ブチル、ＣＨＣＨ_３－ＣＯ－ＣＨ_３、シクロヘキシル、又はフェニルを表し、
Ｒ^２は、水素、ハロゲン、Ｃ_１～Ｃ_６－アルキル、又はＣ_１～Ｃ_６－アルケニルを表し、
Ｒ^３は、電子吸引性基、好ましくは－Ｆ、－Ｃｌ、－Ｂｒ、－Ｉ、－ＮＯ、ＮＯ_２、－ＣＦ_３、－ＯＣＦ_３、－ＣＮ、－ＳＣＮ、－ＮＣＯ、－ＣＮＯ、－ＣＯＣＨ_３、－ＣＯＣＦ_３、－ＣＯ－Ｃ_２Ｆ_５、－ＳＯ_３、－ＳＯ_２－Ｎ（ＣＨ_３）_２、アリールスルホニル、アリールスルフィニル、アリールカルボニル、アルキルカルボニル、アリールオキシカルボニル、又は－ＮＲ^４－ＣＯ－Ｒ^５を表すが、ここでＲ^４及びＲ^５は、同一であっても異なっていてもよく、そしてそれぞれ独立して、以下のものであってよく：Ｈ、Ｃ_１～Ｃ_６－アルキル、ペルハロゲン化Ｃ_１～Ｃ_６－アルキル、アルデヒド、ケトン、エステル、アミド、ニトリル、任意選択により場合によっては置換されたアリール、ピリジニウム－アルキル、ピリジニウム－ペルハロアルキル、又は任意選択により場合によっては置換されたＣ_５～Ｃ_６シクロヘキシル、Ｃ_ｎＨ_２ｎＹ若しくはＣ_ｎＦ_２ｎＹ基（ｎ＝１～６）、そしてＹは、次式（ＥＷＧ１）、（ＥＷＧ２）又は（ＥＷＧ３）の一つのイオン性の基又はラジカルを表し、

（式中、
Ｒ^６、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０、Ｒ^１１は、独立して、Ｈ、Ｃ_１～Ｃ_６－アルキル、Ｃ_１～Ｃ_６－ペルハロアルキル、又はＣ_５～Ｃ_６－アリールを表すが、Ｒ^９、Ｒ^１０、Ｒ^１１が、複素環を形成してもよく、
Ｘ^３は、アニオン、ハロゲン、テトラフルオロボレート（［ＢＦ_４］^－）、［テトラキス－（３，５－ビス（トリフルオロメチル）フェニル）ボレート］（［ＢＡＲＦ］^－）、ヘキサフルオロホスフェート（［ＰＦ_６］^－）、ヘキサフルオロアンチモネート（［ＳｂＦ_６］^－）、ヘキサフルオロアルセネート（［ＡｓＦ_６］^－）、又はトリフルオロメチルスルホネート（［（ＣＦ_３）_２Ｎ］^－）を表す）；
Ｒ^４及びＲ^５は、それらが結合されているＮ及びＣと合体して、次式の（ＥＷＧ４）又は（ＥＷＧ５）の複素環を形成してもよく、

（式中、
ｈａｌは、ハロゲンであり、そして
Ｒ^１２は、水素、Ｃ_１～Ｃ_６－アルキル、Ｃ_５～Ｃ_６－シクロアルキル、又はＣ_５～Ｃ_６－アリールである）、
Ｌは、一般式（Ｌ１）又は（Ｌ２）のＮＨＣ配位子を表す、

（式中、
Ｒ^１３は、水素、Ｃ_１～Ｃ_６－アルキル、Ｃ_３～Ｃ_３０－シクロアルキル、又はＣ_５～Ｃ_３０－アリールであり、
Ｒ^１４及びＲ^１５は、同一であっても異なっていてもよく、そして直鎖状又は分岐状のＣ_３～Ｃ_３０－アルキル、Ｃ_３～Ｃ_３０－シクロアルキル、Ｃ_５～Ｃ_３０－アリール、Ｃ_５～Ｃ_３０－アルクアリール、Ｃ_５～Ｃ_３０－アラルキル、任意選択により場合によっては３個までのヘテロ原子を含み、好ましくはイソプロピル、ｉ－ブチル、ｔｅｒｔ－ブチル、シクロヘキシル、又はフェニルである。）］ Accordingly, the problem addressed by the present invention can be solved by a process for reducing the molecular weight of nitrile rubbers, wherein in a metathesis reaction nitrile rubbers are converted to ruthenium compounds of general formula (IA) Contact with complex catalyst:

[In the formula,
X ¹ and X ² , which may be the same or different, represent an anionic ligand, preferably halogen, more preferably F, Cl, Br, I, particularly preferably Cl,
R ¹ is linear or branched aliphatic C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, C ₅ -C ₂₀ -aryl, CHCH ₃ -CO-CH ₃ , preferably methyl , ethyl, isopropyl, isoamyl, t-butyl, CHCH ₃ —CO—CH ₃ , cyclohexyl, or phenyl;
R ² represents hydrogen, halogen, C ₁ -C ₆ -alkyl or C ₁ -C ₆ -alkenyl,
R ³ is an electron-withdrawing group, preferably -F, -Cl, -Br, -I, -NO, NO ₂ , -CF ₃ , -OCF ₃ , -CN, -SCN, -NCO, -CNO, - COCH ₃ , —COCF ₃ , —CO—C ₂ F ₅ , —SO ₃ , —SO ₂ —N(CH ₃ ) ₂ , arylsulfonyl, arylsulfinyl, arylcarbonyl, alkylcarbonyl, aryloxycarbonyl, or —NR ⁴ represents —CO—R ⁵ where R ⁴ and R ⁵ may be the same or different and each independently may be: H, C ₁ -C ₆ -alkyl, perhalogenated C ₁ -C ₆ -alkyl, aldehyde, ketone, ester, amide, nitrile, optionally optionally substituted aryl, pyridinium-alkyl, pyridinium-perhaloalkyl, or optionally optionally is a substituted C ₅ -C ₆ cyclohexyl, C _n H _2n Y or C _n F _2n Y group (n=1-6), and Y is one of the following formulas (EWG1), (EWG2) or (EWG3) represents an ionic group or radical,

(In the formula,
R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ are independently H, C ₁ -C ₆ -alkyl, C ₁ -C ₆ -perhaloalkyl or C ₅ -C ₆ -aryl represents, R ⁹ , R ¹⁰ and R ¹¹ may form a heterocyclic ring,
X ³ is an anion, halogen, tetrafluoroborate ([BF ₄ ] ⁻ ), [tetrakis-(3,5-bis(trifluoromethyl)phenyl)borate] ([BARF] ⁻ ), hexafluorophosphate ([PF ₆ ] ⁻ ), hexafluoroantimonate ([SbF ₆ ] ⁻ ), hexafluoroarsenate ([AsF ₆ ] ⁻ ), or trifluoromethylsulfonate ([(CF ₃ ) ₂ N] ⁻ ));
R ⁴ and R ⁵ may be combined with the N and C to which they are attached to form a heterocyclic ring of (EWG4) or (EWG5) of the formula

(In the formula,
hal is halogen and R ¹² is hydrogen, C ₁ -C ₆ -alkyl, C ₅ -C ₆ -cycloalkyl, or C ₅ -C ₆ -aryl),
L represents an NHC ligand of general formula (L1) or (L2);

(In the formula,
R ¹³ is hydrogen, C ₁ -C ₆ -alkyl, C ₃ -C ₃₀ -cycloalkyl or C ₅ -C ₃₀ -aryl,
R ¹⁴ and R ¹⁵ can be identical or different and are linear or branched C ₃ -C ₃₀ -alkyl, C ₃ -C ₃₀ -cycloalkyl, C ₅ -C ₃₀ -aryl , C ₅ -C ₃₀ -alkaryl, C ₅ -C ₃₀ -aralkyl, optionally containing up to 3 heteroatoms, preferably isopropyl, i-butyl, tert-butyl, cyclohexyl or phenyl be. )]

It should be noted at this point that in the context of the present invention, heretofore and hereinafter, the definitions and parameters of the groups indicated in general terms or in preferred, more preferred, particularly preferred and most preferred regions are meant to include each other in any desired combination.

Preferred NHC ligands are L1a, L2a, L1b, L2b, L1c, L2c, L1d, L2d, L1e and L2e.

More preferred NHC ligands are L1a, L2a, L1b, L2b, L1c, or L2c.

A particularly preferred NHC ligand is L1a or L2a.

R ³ is preferably: -F, -Cl, -Br, -I, -NO, -NO ₂ , -CF ₃ , -OCF ₃ , -CN, -SCN, -NCO, - CNO, -COCH ₃ , -COCF ₃ , -CO-C ₂ F ₅ , -SO ₃ , -SO ₂ N(CH ₃ ) ₂ , -NHCO-H, -NH-CO-CH ₃ , -NH-CO- CF ₃ , —NHCO—OEt, —NHCO—OiBu, —NH—CO—COOEt, —CO—NR ₂ , —NH—CO—C ₆ F ₅ , —NH(CO—CF ₃ ) ₂ .

R ³ is more preferably -Cl, -Br, -NO ₂ , -NH-CO-CF ₃ , -NH-CO-OiBu, -NH-CO-COOEt.

R ³ is particularly preferably -NH-CO-CF ₃ , -NH-CO-OiBu, NH-CO-COOEt.

Preferred ruthenium complex catalysts are:

More preferred ruthenium complex catalysts are M71 SIPr, M73 SIPr, and M74 SIPr.

A particularly preferred ruthenium complex catalyst is M73 SIPr.

In molecular weight reduction in the present invention, the amount of ruthenium complex catalyst of general formula (IA) or (IB) used, based on the nitrile rubber used, depends on the nature and catalytic activity of the particular ruthenium complex catalyst. do. The amount of ruthenium complex catalyst used is typically from 1 ppm to 1000 ppm, preferably from 2 ppm to 500 ppm, especially from 5 ppm to 250 ppm of noble metal, based on the nitrile rubber used.

Metathesis of NBR can be carried out in the absence or otherwise in the presence of co-olefins. The co-olefin is preferably a linear or branched C ₂ -C ₁₆ olefin. Suitable examples are ethylene, propylene, isobutene, styrene, 1-dodecene, 1-hexene or 1-octene. Preference is given to using 1-hexene or 1-octene. When the coolefin is liquid (such as 1-hexene), the amount of coolefin preferably ranges from 0.2% to 20% by weight, based on the nitrile rubber used. is within. When the co-olefin is gaseous, for example ethylene, the amount of co-olefin is in the reaction vessel at room temperature at a pressure in the range of 1×10 ⁵ Pa to 1×10 ⁷ Pa, preferably is selected to obtain a pressure in the range of 5.2×10 ⁵ Pa to 4×10 ⁶ Pa.

The metathesis reaction can be carried out in a suitable solvent that does not deactivate the catalyst used or adversely affect the reaction in any way. Suitable solvents include, but are not limited to, dichloromethane, benzene, toluene, methyl ethyl ketone, acetone, tetrahydrofuran, tetrahydropyran, dioxane, cyclohexane, monochlorobenzene, and the like. A particularly preferred solvent is monochlorobenzene. In some cases it may be possible to dispense with the addition of further additional solvent if the co-olefin itself can function as a solvent, for example in the case of 1-hexene.

There is no hard limit on the concentration of nitrile rubber used in the reaction mixture for metathesis, unless the viscosity of the reaction mixture is so high that mixing problems are involved. It should be noted that the reaction may be adversely affected. The concentration of NBR in the reaction mixture is preferably in the range of 1 wt% to 30 wt%, more preferably in the range of 5 wt% to 25 wt%, based on the total reaction mixture.

Metathetic degradation is typically carried out at temperatures in the range 10°C to 150°C, preferably in the range 20°C to 100°C.

The reaction time depends on several factors, such as the type of NBR, the type of catalyst, the catalyst concentration used, and the reaction temperature. Typically, the reaction is complete within 5 hours under normal conditions. The progress of metathesis can be monitored by standard analytical methods, for example by gel permeation chromatography (GPC) measurements, or by measuring viscosity.

The nitrile rubber (“NBR”) used in the process of the present invention comprises at least one conjugated diene, at least one α,β-unsaturated nitrile, and optionally one or more further copolymerizable It may be a binary, ternary, or quaternary polymer comprising repeating units of monomers.

Various conjugated dienes can be used. Conjugated ( _C4 - _C6 ) dienes are preferably used. Particularly preferred are 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene, or mixtures thereof. Especially preferred are 1,3-butadiene and isoprene or mixtures thereof. Very particular preference is given to 1,3-butadiene.

The α,β-unsaturated nitrile used can be any of the known α,β-unsaturated nitriles, including (C ₃ -C ₅ )-α,β-unsaturated nitriles such as acrylonitrile (ACN) , methacrylonitrile, ethacrylonitrile or mixtures thereof are preferred. Acrylonitrile is particularly preferred.

A particularly preferred nitrile rubber is therefore a copolymer of acrylonitrile and 1,3-butadiene.

As well as conjugated dienes and α,β-unsaturated nitriles, one or more further copolymerizable monomers known to those skilled in the art, such as α,β-unsaturated monocarboxylic or dicarboxylic acids, or esters or amides thereof It is also possible to use

Preferred α,β-unsaturated mono- or di-carboxylic acids herein are fumaric acid, maleic acid, acrylic acid and methacrylic acid.

Esters of α,β-unsaturated carboxylic acids that are used include the following:
Alkyl (meth)acrylates, especially C ₁ -C ₁₈ -alkyl (meth)acrylates, preferably n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-(meth)acrylate pentyl or n-hexyl (meth)acrylate;
alkoxyalkyl (meth)acrylates, in particular C ₁ -C ₁₈ -alkoxyalkyl (meth)acrylates, preferably C ₄ -C ₁₂ -alkoxyalkyl (meth)acrylates;
hydroxyalkyl (meth)acrylates, in particular C ₁ -C ₁₈ -hydroxyalkyl (meth)acrylates, preferably C ₄ -C ₁₂ -hydroxyalkyl (meth)acrylates;
Cycloalkyl (meth)acrylates, in particular C ₅ -C ₁₈ -cycloalkyl (meth)acrylates, preferably C ₆ -C ₁₂ -cycloalkyl (meth)acrylates, more preferably (meth)acrylic acid cyclopentyl, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate;
Alkylcycloalkyl (meth)acrylates, in particular C ₆ -C ₁₂ -alkylcycloalkyl (meth)acrylates, preferably C ₇ -C ₁₀ -alkylcycloalkyl (meth)acrylates, more preferably (meth)acrylates ) methylcyclopentyl acrylate and ethylcyclohexyl (meth)acrylate;
aryl monoesters, in particular C ₆ -C ₁₄ -aryl monoesters, preferably phenyl (meth)acrylate or benzyl (meth)acrylate;
- amino-containing α,β-ethylenically unsaturated carboxylic acid esters, such as dimethylaminomethyl acrylate or diethylaminoethyl acrylate;
- a dicarboxylate of an α,β-ethylenically unsaturated monoalkyl, preferably
Alkyl monoesters, especially C ₄ -C ₁₈ -alkyl monoesters, preferably n-butyl, tert-butyl, n-pentyl or n-hexyl monoesters, more preferably mono-n-butyl maleate, fumaric acid mono-n-butyl, mono-n-butyl citraconate, mono-n-butyl itaconate, most preferably mono-n-butyl maleate;
alkoxyalkyl monoesters, especially C ₄ -C ₁₈ -alkoxyalkyl monoesters, preferably C ₄ -C ₁₂ -alkoxyalkyl monoesters,
hydroxyalkyl monoesters, especially C ₄ -C ₁₈ -hydroxyalkyl monoesters, preferably C ₄ -C ₁₂ -hydroxyalkyl monoesters,
cycloalkyl monoesters, especially C ₅ -C ₁₈ -cycloalkyl monoesters, preferably C ₆ -C ₁₂ -cycloalkyl monoesters, more preferably monocyclopentyl maleate, monocyclohexyl maleate, monocycloheptyl maleate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocycloheptyl fumarate, monocyclopentyl citraconate, monocyclohexyl citraconate, monocycloheptyl citraconate, monocyclopentyl itaconate, monocyclohexyl itaconate, and monocycloheptyl itaconate,
Alkyl cycloalkyl monoesters, especially C ₆ -C ₁₂ -alkyl cycloalkyl monoesters, preferably C ₇ -C ₁₀ -alkyl cycloalkyl monoesters, more preferably monomethylcyclopentyl maleate and monoethylcyclohexyl maleate, fumaric acid monomethylcyclopentyl and monoethylcyclohexyl fumarate, monomethylcyclopentyl citraconate and monoethylcyclohexyl citraconate; monomethylcyclopentyl itaconate and monoethylcyclohexyl itaconate,
Aryl monoesters, especially C ₆ -C ₁₄ -aryl monoesters, preferably monoaryl maleate, monoaryl fumarate, monoaryl citraconate or monoaryl itaconate, more preferably monophenyl maleate or monoaryl maleate benzyl, monophenyl fumarate or monobenzyl fumarate, monophenyl citraconate or monobenzyl citraconate, monophenyl itaconate or monobenzyl itaconate,
• Unsaturated polyalkylpolycarboxylic acids such as dimethyl maleate, dimethyl fumarate, dimethyl itaconate or diethyl itaconate.

Mixtures of the aforementioned esters can also be used.

［式中、
Ｒは、非分岐状又は分岐状のＣ_１～Ｃ_２０－アルキル、好ましくはＣ_２～Ｃ_２０－アルキル、より好ましくはエチル、ブチル、又はエチルヘキシルであり、
ｎは、２～１２、好ましくは２～８、より好ましくは２～５、最も好ましくは２又は３であり、そして
Ｒ^１は、水素又はＣＨ_３－である］
から誘導されるＰＥＧアクリレートである。 The esters of α,β-unsaturated carboxylic acids used are preferably their alkyl and alkoxyalkyl esters. Particularly preferred alkyl esters of α,β-unsaturated carboxylic acids are methyl acrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and octyl acrylate. . Particularly preferred alkoxyalkyl esters of α,β-unsaturated carboxylic acids are methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate. Preferred α,β-ethylenically unsaturated carboxylic acid esters for use are further represented by general formula (I)

[In the formula,
R is unbranched or branched C ₁ -C ₂₀ -alkyl, preferably C ₂ -C ₂₀ -alkyl, more preferably ethyl, butyl or ethylhexyl,
n is 2-12, preferably 2-8, more preferably 2-5, most preferably 2 or 3, and R ¹ is hydrogen or CH ₃ —]
is a PEG acrylate derived from

The term "(meth)acrylate" stands for "acrylate" and "methacrylate" in the context of the present invention. When the R ¹ group in general formula (I) is CH ₃ —, the molecule is a methacrylate.

The term "polyethylene glycol" or "PEG" for short, in the context of the present invention, ranges from 2 repeating ethylene glycol units (PEG-2; n=2) to 12 repeating ethylene glycol units (PEG-2 to PEG-12; n=2-12).

The term "PEG acrylate" is also abbreviated PEG-X-(M)A, where "X" is the number of repeating units of ethylene glycol, "MA" is methacrylate, and "A" is an acrylate.

Acrylate units derived from PEG acrylates of general formula (I) are referred to as "PEG acrylate units" in the context of the present invention.

A preferred PEG acrylate unit is no. 1 to no. PEG acrylate with 8, where n is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, preferably 2, 3, 4, 5, 6, 7 or 8, more preferably 2, 3, 4 or 5, most preferably 2 or 3.

Other commonly used designations for ethoxy polyethylene glycol acrylate (formula no. 1) are, for example, poly(ethylene glycol) ethyl ether acrylate, ethoxy PEG acrylate, ethoxy poly(ethylene glycol) monoacrylate, or poly (ethylene glycol) monoethyl ether monoacrylate and the like.

These PEG acrylates are commercially available, for example sold by Arkema under the trade name Sartomer®, by Evonik under the trade name Visiomer®, or by Sigma Aldrich.

In one preferred embodiment, the amount of PEG acrylate units in the nitrile rubber is from 0 wt% to 65 wt%, preferably from 20 wt% to 60% by weight, more preferably 20% to 55% by weight.

In another embodiment, the amount of PEG acrylate in the nitrile rubber is 20% to 60% by weight based on the total amount of all monomer units of 100% by weight, and PEG acrylate is The amount of different α,β-ethylenically unsaturated carboxylic acid ester units is from 0% to 40% by weight, provided that the total amount of carboxylic acid ester units does not exceed 60% by weight.

In another embodiment, the nitrile rubber contains not only α,β-ethylenically unsaturated nitrile units, conjugated diene units, and PEG acrylate units derived from PEG acrylates of general formula (I), but also unsaturated Also included as carboxylic acid ester units are monoalkyldicarboxylate units, preferably monobutyl maleate.

In one preferred nitrile rubber, the α,β-ethylenically unsaturated nitrile units are derived from acrylonitrile or methacrylonitrile, more preferably acrylonitrile, and the conjugated diene units are derived from isoprene or 1,3-butadiene. , more preferably derived from 1,3-butadiene, and whose α,β-ethylenically unsaturated carboxylic acid ester units are exclusively from PEG acrylates of general formula (I) wherein n is 2 to 8, more preferably is a PEG acrylate unit derived from a PEG acrylate of general formula (I) where n is 2 or 3, wherein no further carboxylic acid ester units are present.

In further preferred nitrile rubbers, the α,β-ethylenically unsaturated nitrile units are derived from acrylonitrile or methacrylonitrile, more preferably acrylonitrile, and the conjugated diene units are derived from isoprene or 1,3-butadiene, more preferably derived from 1,3-butadiene and whose α,β-ethylenically unsaturated carboxylic acid ester units are from a first PEG acrylate of general formula (I) wherein n is 2 to 12, more preferably is derived from PEG acrylates of general formula (I) where n is 2 or 3, and α,β-ethylenically unsaturated carboxylic acid ester units other than PEG acrylate units.

In addition, the nitrile rubber contains from 0% to 20% by weight, preferably 0%, of one or more further copolymerizable monomers, based on the total amount of all monomer units of 100% by weight. .1% to 10% by weight. In that case, the amounts of other monomeric units are reduced accordingly so that the sum of all monomeric units is always 100% by weight. The nitrile rubber may contain, as further copolymerizable monomers, one or more from:
- aromatic vinyl monomers, preferably styrene, α-methylstyrene, and vinylpyridine,
Fluorine-containing vinyl monomers, preferably fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-fluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene, and tetrafluoroethylene, etc.
α-olefins, preferably C ₂ -C ₁₂ olefins such as ethylene, 1-butene, 4-butene, 4-methyl-1-pentene, 1-hexene or 1-octene,
non-conjugated dienes, preferably C4- _C12 dienes, such as _1,4 -pentadiene, 1,4-hexadiene, 4-cyanocyclohexene, 4-vinylcyclohexene, vinylnorbornene, dicyclopentadiene, etc.;
- alkynes, such as 1-butyne or 2-butyne,
- an α,β-ethylenically unsaturated monocarboxylic acid, preferably acrylic acid, methacrylic acid, crotonic acid or cinnamic acid,
α,β-ethylenically unsaturated dicarboxylic acids, preferably maleic acid, fumaric acid, citraconic acid, itaconic acid,
Copolymeric antioxidants such as N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)methacrylamide, N-(4-anilinophenyl)cinnamide, N-(4-anilino Phenyl)crotonamide, N-phenyl-4-(3-vinylbenzyloxy)aniline, N-phenyl-4-(4-vinylbenzyloxy)aniline, or Crosslinking monomers such as divinyl moieties such as divinylbenzene.

In yet another embodiment, the nitrile rubber contains, as PEG acrylate units, ethoxy, butoxy, or ethylhexyloxy polyethylene glycol (meth)acrylate containing 2 to 12 repeating ethylene glycol units, more preferably 2 to 5. and most preferably ethoxy or butoxy polyethylene glycol (meth)acrylates containing 2 or 3 repeating ethylene glycol units.

In yet another nitrile rubber embodiment, n is 2 or 3, R is ethyl or butyl, and R ¹ is hydrogen or methyl, but preferably n is 2 and R is butyl and R ¹ is methyl.

In yet another embodiment, the nitrile rubber comprises 8% to 18% by weight acrylonitrile units, 27% to 65% by weight 1,3-butadiene units, and 27% to 55% by weight PEG. -2 acrylate units or PEG-3 acrylate units.

In yet another embodiment, the nitrile rubber includes:
13% to 17% by weight of α,β-ethylenically unsaturated nitrile units, preferably acrylonitrile,
36% to 44% by weight of conjugated diene units, preferably 1,3-butadiene, and 43% to 47% by weight of PEG acrylates derived from PEG acrylates of general formula (I), preferably butoxy Diethylene glycol methacrylate.

The ratio of conjugated diene to α,β-unsaturated nitrile in the NBR polymer used can vary within wide limits. The proportion of conjugated dienes, or their combined proportion, is typically in the range of 40% to 90% by weight, preferably in the range of 55% to 85% by weight, based on the total polymer. The proportion of α,β-unsaturated nitriles, or their combined proportion, typically ranges from 10% to 60%, preferably from 15% to 45% by weight, based on the total polymer. is. In either case, the sum of the proportions of the monomers amounts to 100% by weight. Additional monomers may be present in an amount of 0 wt% to 40 wt%, preferably 0.1 wt% to 65 wt%, more preferably 1 wt% to 30 wt%, based on total polymer. . In this case, the corresponding proportions of conjugated dienes and/or α,β-unsaturated nitriles are replaced by proportions of additional monomers, but in each case the proportions of all monomers add up to 100% by weight.

The preparation of nitrile rubbers by polymerizing the aforementioned monomers is well known to those skilled in the art and is described in detail in the literature (eg W. Hofmann, Rubber Chem. Technol., 36 (1963)).

Nitrile rubbers that can be used in the process of the invention are commercially available products from the product series of the Perbunan® and Krynac® brands, for example from ARLANXEO Deutschland GmbH.

The nitrile rubber used for metathesis has a Mooney viscosity (ML1+4, 100° C.) in the range 30-100, preferably 30-50. This corresponds to a weight-average molecular weight Mw in the range from 150,000 g/mol to 500,000 g/mol, preferably in the range from 180,000 g/mol to 400,000 g/mol. The nitrile rubber used furthermore has a polydispersity in the range 2.0 to 8.0, preferably in the range 2.0 to 6.0, PDI=Mw/Mn, where Mw is the weight average molecular weight, Mn has a number average molecular weight).

Mooney viscosity is determined herein according to ASTM standard D 1646.

The nitrile rubber obtained by the metathesis process in the present invention has a Mooney viscosity (ML1+4@100° C.) in the range of 5-35, preferably in the range of 5-25. This corresponds to a weight-average molecular weight Mw in the range from 10,000 g/mol to 150,000 g/mol, preferably in the range from 10,000 g/mol to 100,000 g/mol. The resulting nitrile rubber furthermore has a polydispersity in the range 1.4 to 4.0, preferably in the range 1.5 to 3.0, PDI=Mw/Mn, where Mn is the number average molecular weight. have.

The present invention further provides the use of ruthenium complex catalysts in metathesis reactions for the metathesis of nitrile rubber. These metathesis reactions may be, for example, ring closing metathesis (RCM), cross metathesis (CM), or otherwise ring opening metathesis (ROMP). Typically for this purpose the nitrile rubber is contacted and reacted with a ruthenium complex catalyst.

Use in the present invention is a process for reducing the molecular weight of nitrile rubber by contacting the nitrile rubber with a ruthenium complex catalyst. This reaction is cross metathesis.

Metathetic cracking in the presence of the catalyst system according to the invention may be followed by hydrogenation of the cracked nitrile rubber so obtained. This can be done in a manner known to those skilled in the art.

The hydrogenation can be carried out using homogeneous or heterogeneous hydrogenation catalysts. It is also possible to carry out the hydrogenation reaction in situ, i.e. in the same reaction mixture in which the metathetic cracking was previously carried out, without the need to isolate the molecular weight-reduced nitrile rubber. . The hydrogenation catalyst is simply added into the reaction vessel.

The catalysts used are typically based on rhodium, ruthenium or titanium, but platinum, iridium, palladium, rhenium, ruthenium, osmium, cobalt or copper as metal or otherwise. can also be used, preferably in the form of metal compounds (e.g. US-A-3,700,637, DE-A-25 39 132, European patent application DE-A-0 134 023, DE-A-35 41 689, DE-A-35 40 918, EP-A-0 298 386, DE-A-35 29 252, DE-A-34 33 392, US-A-4,464,515, and See US Pat. No. 4,503,196).

Suitable catalysts and solvents for hydrogenation in homogeneous phase are described below and are also known from DE-A-2539132 and EP-A-0471250. .

Selective hydrogenation can be achieved, for example, in the presence of rhodium or ruthenium catalysts. For example, it is possible to use catalysts of the following general formula:
(R ¹ _m B) _l MX _{n
wherein M is} ^ruthenium _{or rhodium ;} or a C ₇ -C ₁₅ aralkyl group, B is a phosphorus, arsenic, sulfur or sulfoxide group S═O, X is hydrogen or an anion, preferably halogen, more preferably chlorine or bromine, l is 2, 3 or 4, m is 2 or 3 and n is 1, 2 or 3, preferably 1 or 3. Suitable catalysts are tris(triphenylphosphine)rhodium(I) chloride, tris(triphenylphosphine)rhodium(III) chloride and tris(dimethylsulfoxide)rhodium(III) chloride, as well as tetrakis(triphenylphosphine)rhodium Hydrides of the formula ((C ₆ H ₅ ) ₃ P) ₄ RhH and the corresponding compounds in which triphenylphosphine is wholly or partially substituted by tricyclohexylphosphine. A small amount of catalyst may be used. In the range of 0.01 wt% to 1 wt%, preferably in the range of 0.03 wt% to 0.5 wt%, more preferably 0.05 wt% to 0.3 wt%, based on the weight of the polymer is preferred.

Typically, it is recommended to use the catalyst with a co-catalyst, which co-catalyst is a ligand of formula R ¹ mB, where R ¹ , m and B are each is defined for Preferably m is 3, B is phosphorus and the R ¹ groups may be the same or different. The promoter comprises a trialkyl, tricycloalkyl, triaryl, trialalkyl, diarylmonoalkyl, diarylmonocycloalkyl, dialkylmonoaryl, dialkylmonocycloalkyl, dicycloalkylmonoaryl, or dicycloalkylmonoaryl group. preferably have.

Examples of cocatalysts can be found, for example, in US Pat. No. 4,631,315. A preferred cocatalyst is triphenylphosphine. In addition, the rhodium catalyst to cocatalyst weight ratio is preferably in the range of (1:1) to (1:55), more preferably in the range of (1:3) to (1:30). . Based on 100 parts by weight of nitrile rubber to be hydrogenated, the preferred process comprises 0.1 to 33 parts by weight of cocatalyst, preferably 0.2 parts to 20 parts by weight, even more preferably 0.5 parts by weight. parts to 5 parts by weight, in particular more than 0.9 parts by weight and less than 5 parts by weight of cocatalyst, based on 100 parts by weight of nitrile rubber to be hydrogenated.

The practical implementation of this hydrogenation is also well known to those skilled in the art from US-A-6,683,136. It typically involves hydrogenating a nitrile rubber with hydrogen in a solvent such as toluene or monochlorobenzene at a temperature ranging from 100° C. to 150° C. and a pressure ranging from 5 MPa to 15 MPa for 2 hours to It is carried out by contacting for 10 hours.

In the context of the present invention, hydrogenation means that the double bonds present in the starting nitrile rubber are removed in a proportion of at least 50%, preferably 70% to 100%, more preferably 80% to 100%. It should be understood that it means to convert. Furthermore, it is particularly preferred that the residual content of double bonds in HNBR is between 0% and 8%.

When heterogeneous catalysts are used, they are typically supported catalysts based on palladium, for example on charcoal, silica, calcium carbonate or barium sulfate.

Upon completion of hydrogenation, a hydrogenated nitrile rubber is obtained, which has a Mooney viscosity (ML1+4 @ 100°C) in the range of 1-50 as measured by ASTM standard D1646. This roughly corresponds to a weight average molecular weight Mw in the range of 2000 to 400,000 g/mol. It is preferable if the Mooney viscosity (ML1+4@100° C.) is in the range of 5-40. This roughly corresponds to a weight average molecular weight Mw in the range of 20,000 to 200,000 g/mol. Furthermore, the hydrogenated nitrile rubber so obtained has a polydispersity in the range 1 to 5, preferably in the range 1.5 to 3, PDI=Mw/Mn, where Mw is the weight average molecular weight, Mn is the number average molecular weight).

I. Description of analytical methods Gel Permeation Chromatography (GPC) procedure:
Molecular weights M _n and M _w are determined using the following equipment and are calculated by means of Waters Empower 2 Data Base Software: Shimadzu LC-20AT high performance liquid chromatography (HPLC) pump, SFD S5200 autosampler, 3 PLgel 10 μm Mixed-B column (300×7.5 mm ID), Shodex RI-71 detector, ERC column oven. GPC experiments were performed at 40° C. using tetrahydrofuran (THF) flow rate of 1 mL/min as the eluent. The GPC column was calibrated using standard polystyrene (PS) samples.

Determination of residual double bond (“RDB”) content:
RDB (units, %) is determined by means of the following FT-IR method: Before, during and after the hydrogenation reaction, the spectra of the nitrile rubber are taken by means of a Thermo Nicolet FT-IR spectrometer of the AVATAR 360 type. ,Record. A solution of NBR in monochlorobenzene was coated onto a NaCl plate to prepare a membrane for analysis. Hydrogenation rate is determined by means of FT-IR analysis according to ASTM standard D5670-95.

Measurement of Mooney viscosity:
Mooney viscosity measurements are determined by the method of ASTM Standard D1646. Mooney viscosity (ML1+4 @ 100°C) was measured at 100°C with a preheating time of 1 minute and a measurement time of 4 minutes.

Measurement of Brookfield viscosity:
Solution viscosity of a solution of polymer in MCB is measured using a Brookfield LV DV II+ rotational viscometer. The measurements were performed in a 400 mL beaker filled with 250 mL of polymer solution at a temperature of 23±0.1° C. using a #62 standard spindle.

II. Materials Used Table 1 summarizes the non-inventive catalysts used in the examples described hereinafter (Grubbs II, Grubbs-Hoveyda II, Zhan 1B, M71 SIMes, and M73 SIMes).

Table 2 summarizes the catalysts of the invention used in the examples described hereinafter (M71 SIPr, M73 SIPr, M74 SIPr).

Explanation of symbols:
Ph represents in each case a phenyl group.
Dipp represents in each case a diisopropylphenyl group.
Mes represents in each case a 2,4,6-trimethylphenyl group.

Nitrile Rubbers Used The examples described below were carried out using various NBRs and HNBRs from ARLANXEO Deutschland GmbH. Those nitrile rubbers had the property values shown in Table 3.

III. Metathesis reaction:
Table 5 summarizes the inventive examples and the corresponding non-inventive reference examples, where the inventive examples are marked with an asterisk (*).

In Examples 1a-8b ^* and 12 ^* -17 ^* , the nitrile rubber degradation was carried out in the form of cross metathesis using an additive of 1-hexene. In the inventive examples and the corresponding reference examples, the catalyst was used such that the ruthenium loading was in each case 9 ppm and 18 ppm.

In Examples 9, 10 ^* , and 11, nitrile rubber degradation was carried out in the form of self-metathesis without the addition of 1-hexene. These examples were run with a ruthenium loading of 67 ppm.

In Examples 17 ^* and 18 metathesis of partially hydrogenated nitrile rubber was performed. The metathesis was carried out at 151 ppm ruthenium dosage and 100° C. with no 1-olefin additive (self-metathesis).

Procedure for metathesis reaction:
All metathesis reactions were carried out in solution using monochlorobenzene (manufactured by Aldrich, hereinafter referred to as MCB). MCB was distilled and inerted by passing nitrogen through it at room temperature before use. The amount of nitrile rubber shown in the table below was dissolved in the MCB with stirring for 12 hours at room temperature. Additives (olefins) shown in the table were added to the rubber-containing solution and stirred for 2 hours to homogenize. For experiments with additives, the additive was added at this point and the rubber-containing solution was stirred for an additional hour. Prior to adding the catalyst, the rubber solution in monochlorobenzene was heated to the temperature indicated in the table. Reaction mixtures 1-11 were made to have a post-catalyst rubber concentration of 15% by weight, and reaction mixtures 12 and 13 were made to have a post-catalyst rubber concentration of 10% by weight.

The metathesis catalysts (see Table 1) were respectively dissolved in 1 mL (0.0066 mmol catalyst) or 2 mL (0.013 mM catalyst) of MCB and immediately added to the nitrile rubber solution. Addition of the catalyst initiated the metathesis reaction, which was monitored by measuring the average molecular weight by means of gel permeation chromatography at regular time intervals (1 hour, 3 hours, 24 hours). The reaction was stopped by immediately adding 0.8 mL of ethyl vinyl ether to the samples taken for molecular weight determination (5 mL each time). The viscosity of the final sample (after a reaction time of 24 hours) was also measured in solution using a Brookfield viscometer (measuring temperature: 21°C).

Examples of the present invention and comparative examples
Examples 1a and b : Reaction of NBR with Grubbs II catalyst

Examples 2a and b : Reaction of NBR with Grubbs-Hoveyda II catalyst

Examples 3a and b : Reaction of NBR with Zhan 1B catalyst

Examples 4a and b : Reaction of NBR with M71 SIMes catalyst

Example 5a ^* and b ^* : Reaction of NBR with M71 SIPr catalyst

Examples 6a and b : Reaction of NBR with M73 SIMes catalyst

Example 7a ^* and b ^* : Reaction of NBR with M73 SIPr catalyst

Example 8a ^* and b ^* : Reaction of NBR with M74 SIPr catalyst

Example 9 : Reaction of NBR with M73 SIMes catalyst without olefins

Example 10 ^* : Reaction of NBR with M73 SIPr catalyst without olefin

Example 11 : Reaction of NBR with Grubbs-Hoveyda II catalyst without olefins

Examples 12 ^* -16 ^* : Reaction of NBR with M71 SIPr or M73 SIPr catalyst and additives in the presence of olefins

Example 17 ^* : Reaction of HNBR with M73 SIPr catalyst without olefin

Example 18 : Reaction of HNBR with Grubbs-Hoveyda II catalyst without olefins

Inventive Examples 5a ^* , 5b ^* , 7a ^* , 7b ^* , 8a ^* , and 8b ^* used the catalysts M71 SIPr, M73 SIPr, and M74 SIPr in the cross metathesis of nitrile rubber with 1-hexene. Then, after a reaction time of 24 hours, non-inventive Examples 1a, 1b, 2a, 2b, 3a, 3b, using Grubbs-II, Grubbs-Hoveyda, Zhan 1B, M71 SIMes, and M73 SIMes catalysts, 4a, 4b, 6a and 6b, giving lower molar masses (M _w and M _n ). The lower molar mass was achieved at both 9 ppm Ru and 18 ppm Ru catalyst loadings.

In addition, in order to equalize the final molar masses of the nitrile rubbers, the catalysts Grubbs-II, Grubbs-Hoveyda, Zhan 1B , M71 SIMes, and M73 SIMes, it is possible to use less ruthenium. By reducing the amount of expensive precious metals, the cross metathesis of nitrile rubber can be made more cost-effective.

Examples 9, 10 ^* , and 11 demonstrate the use of the M73 SIPr of the present invention for self-metathesis of nitrile rubber (without addition of 1-olefin as co-olefin) when using the same ruthenium dosage of 67 ppm ( In Example 10 ^* ), the molar masses (M _w and M _n ) of the nitrile rubber after 24 hours of reaction time were lower than when using M73 SIMes (Example 9) and Grubbs-Hoveyda II (Example 11). indicates that it will be lower. Example 10 ^* shows that the use of the catalyst M73 SIPr of the present invention makes it possible to use ruthenium more economically than currently used catalysts for the metathesis of nitrile rubber. there is

Example 17 ^* In the auto-metathesis of partially hydrogenated nitrile rubber, using the inventive catalyst M73 SIPr, compared to using the Grubbs-Hoveyda II catalyst (Example 18), after 24 hours a lower It shows that the molar masses (M _w and M _n ) are obtained. The use of the catalyst M73 SIPr of the present invention allows economical use of the expensive precious metal ruthenium.

IV. Hydrogenation Subsequent hydrogenation was carried out using NBR-8 from ARLANXEO Deutschland GmbH with the properties shown in Table 2.

Hydrogenation Procedure Dehydrated monochlorobenzene (MCB) was purchased from VWR and used as received. The results of the hydrogenation experiments are summarized in Table 7.

Hydrogenations 1-4 ^* were carried out in a 10 L high pressure reactor under the following conditions:
Solvent: Monochlorobenzene Substrate: NBR-8
Solids content: 12 wt% NBR-8 in MCB (518g)
Reactor temperature: 137°C to 140°C
Reaction time: 4 hours Catalyst usage: 0.2027 g (0.04 phr)
Hydrogen pressure (pH ₂ ): 8.4 MPa
Stirrer speed: 600 rpm

The polymer solution containing NBR-8 is degassed three times with H ₂ (23° C., 2.0 MPa) under vigorous stirring. The reactor temperature was increased to 100° C. and the H ₂ pressure to 60 bar. 50 g of a solution of catalyst (0.2027 g) in monochlorobenzene was added and the pressure was increased to 8.4 MPa while the reactor temperature was adjusted to 138°C. Both parameters were kept constant throughout the reaction. The progress of the reaction was monitored by means of measuring the residual double bond content (RDB) of the nitrile rubber by means of IR spectrophotometry. After 4 hours the reaction was terminated by releasing the hydrogen pressure.

In the examples given above, the hydrogenation over the catalysts M73 SIPr and M71 SIPr of the present invention was at least as good or significantly better than with the catalysts M73SIMes and M71 SIMe under comparable experimental conditions. showing rapid progress.

Claims (15)

A process for reducing the molecular weight of a nitrile rubber, said nitrile rubber , in the presence or absence of a co-olefin, having the general formula (IA)

[In the formula,
X ¹ and X ² represent an anionic ligand selected from halogen , which may be the same or different,
R ¹ represents linear or branched aliphatic C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, C ₅ -C ₂₀ -aryl or CHCH ₃ -CO-CH ₃ ,
R ² represents hydrogen, halogen, C ₁ -C ₆ -alkyl or C ₁ -C ₆ -alkenyl,
R ³ is -F, -Cl, -Br, -I, -NO, -NO ₂ , -CF ₃ , -OCF ₃ , -CN, -SCN, -NCO, -CNO, -COCH ₃ , -COCF ₃ , —CO—C ₂ F ₅ , —SO ₃ , —SO ₂ —N(CH ₃ ) ₂ , arylsulfonyl, arylsulfinyl, arylcarbonyl, alkylcarbonyl, aryloxycarbonyl, and —NR ⁴ —CO—R ⁵ represents an electron-withdrawing group selected from the group consisting of R ⁴ and R ⁵ , which may be the same or different, and each independently may be: H, C ₁ -C ₆ -alkyl, C ₁ -C ₆ -alkyl perhalogenides, aldehydes, ketones, esters, amides, nitriles , substituted or unsubstituted aryls, pyridinium-alkyls, pyridinium-perhaloalkyls, or chlohexyl, a C _n H _2n Y or C _n F _2n Y group (n=1-6), and Y is an ionic group or radical of one of the formulas (EWG1), (EWG2) or (EWG3); represent,

(In the formula,
R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ are independently H, C ₁ -C ₆ -alkyl, C ₁ -C ₆ -perhaloalkyl or C ₅ -C ₆ -aryl represents, R ⁹ , R ¹⁰ and R ¹¹ may form a heterocyclic ring,
X ³ is an anion, halogen, tetrafluoroborate ([BF ₄ ] ⁻ ), [tetrakis-(3,5-bis(trifluoromethyl)phenyl)borate] ([BARF] ⁻ ), hexafluorophosphate ([PF ₆ ] ⁻ ), hexafluoroantimonate ([SbF ₆ ] ⁻ ), hexafluoroarsenate ([AsF ₆ ] ⁻ ), or trifluoromethylsulfonate ([(CF ₃ ) ₂ N] ⁻ ));
R ⁴ and R ⁵ may be combined with the N and C to which they are attached to form a heterocyclic ring of (EWG4) or (EWG5) of the formula

(In the formula,
hal is halogen and R ¹² is hydrogen, C ₁ -C ₆ -alkyl, C ₅ -C ₆ -cycloalkyl or C ₅ -C ₆ -aryl),
L represents an NHC ligand of general formula (L1) or (L2),

(In the formula,
R ¹³ is hydrogen, C ₁ -C ₆ -alkyl, C ₃ -C ₃₀ -cycloalkyl or C ₅ -C ₃₀ -aryl,
R ¹⁴ and R ¹⁵ may be the same or different and are straight-chain or branched C ₃ -C ₃₀ -alkyl, C ₃ -C ₃₀ containing from 0 to 3 heteroatoms. -cycloalkyl, C ₅ -C ₃₀ -aryl, C ₅ -C ₃₀ -alkaryl and C ₅ -C ₃₀ -aralkyl . )]
A process characterized by contacting and reacting with a ruthenium complex catalyst of L is represented by formulas L1a, L2a, L1b, L2b, L1c, L2c, L1d, L2d, L1e, and L2e

A process for reducing the molecular weight of nitrile rubber according to claim 1, characterized in that it corresponds to the NHC ligand of 3. The process for reducing the molecular weight of nitrile rubbers according to claim 1 or 2, characterized in that said NHC ligand meets the formula L1a, L2a, L1b, L2b, L1c, or L2c . R ³ of the electron withdrawing group is -F, -Cl, -Br, -I, -NO, -NO ₂ , -CF ₃ , -OCF ₃ , -CN, -SCN, -NCO, -CNO, - _COCH3 , _-COCF3 , -CO- _C2F5 , _-SO3 , _-SO2N ( _CH3 ) ₂ , _-NHCO -H, -NH-CO- _CH3 , -NH-CO-CF3 _, -NHCO-OEt, -NHCO-OiBu, -NH-CO-COOEt, -CO-NR ₂ , -NH-CO-C ₆ F ₅ , or -NH(CO-CF ₃ ) ₂ , a process for reducing the molecular weight of a nitrile rubber according to any one of claims 1-3. R ³ of the electron withdrawing group is -Cl, -Br, -NO ₂ , -NH-CO-CF ₃ , -NH-CO-OiBu, or -NH-CO-COOE t , a process for reducing the molecular weight of a nitrile rubber according to any one of claims 1-4. X ¹ and X ² are the same or different and represent anionic ligands selected from F, Cl, Br and I; and
R. ¹ is a linear or branched aliphatic C ₁ ～C ₂₀ -alkyl, C ₃ ～C ₂₀ -cycloalkyl, C ₅ ～C ₂₀ -aryl, CHCH ₃ -CO-CH ₃ , cyclohexyl, or phenyl, or a linear or branched aliphatic C selected from the group consisting of methyl, ethyl, isopropyl, isoamyl, and t-butyl. ₁ ～C ₂₀ A process according to any one of claims 1 to 5, which represents -alkyl. The ruthenium complex catalyst has the following formula:

A process for reducing the molecular weight of nitrile rubber according to any one of claims 1 to 6 , characterized in that it meets one of 8. The process for reducing the molecular weight of nitrile rubber according to claim 7 , characterized in that said ruthenium complex catalyst is M71 SIPr, M73 SIPr, or M74 SIPr . The molecular weight of the nitrile rubber according to any one of claims 1 to 8 , wherein the amount of said catalyst used is such that it results in 5 to 1000 ppm of precious metal, based on said nitrile rubber used. process to reduce. 10. A method according to any one of claims 1 to 9 , carried out in the presence of a co-olefin selected from the group consisting of ethylene , propylene, butylene, styrene, 1-dodecene, 1-hexene and 1-octene. process for reducing the molecular weight of nitrile rubber. Nitrile rubber according to any one of claims 1 to 10 , wherein the concentration of the nitrile rubber in the reaction mixture ranges from 1% to 30% by weight, based on the total reaction mixture. Process for reducing molecular weight. Process for reducing the molecular weight of nitrile rubber according to any one of claims 1-11 , carried out at a temperature in the range from 10°C to 150°C. 13. Any one of claims 1 to 12 , wherein one or more further copolymerizable monomers are used, the copolymerizable monomers being selected from α,β-unsaturated mono- or dicarboxylic acids or esters thereof or imides thereof. A process for reducing the molecular weight of the nitrile rubber of claim 1 . The molecular weight of the nitrile rubber according to any one of claims 1 to 13 , wherein the metathesis reaction of the nitrile rubber is followed by a hydrogenation reaction of unsaturated C=C double bonds in the nitrile rubber. process to reduce Use of a ruthenium complex catalyst of general formula (IA) as defined in claim 1 in metathesis reactions for the metathesis of nitrile rubber.